Research status on preparation and properties of RE hafnates for thermal/environmental barrier coatings

The types，preparation methods，thermal and mechanical properties of rare earth hafnate materials and their corrosion behaviors exposed to low melting point silicate（CMAS） and high temperature water vapor are summarized. The previous investigations indicate that the rare earth hafnates have the characteristics of low thermal conductivity，excellent high-temperature phase stability and good resistance to CMAS corrosion，which shows a favorable application prospect in the field of thermal/environmental barrier coatings（T/EBCs）. However，in order to overcome the limitations of a single-phase rare earth hafnate exposed to water vapor corrosion and CMAS，it is still necessary to carry out systematic studies on multi-rare earth components/high-entropy rare earth hafnate in the future，and further clarify the mechanism of influence of lattice distortion caused by components on physical and chemical properties of materials. Moreover，the coupled control method of thermal，mechanical and chemical properties of hafnate with integrated functions such as thermal protection，water vapor corrosion resistance and CMAS resistance and their corresponding material preparation processes should be explored.